Agriculture is a major industry in the U.S., which is a net exporter of food. As of 2009 there were approximately 2.2 million farms in the U.S. covering an area of approximately 920 million acres. Although in 1800 approximately ninety percent of the entire U.S. population was employed in agriculture, present day numbers have dropped to approximately two percent due largely to the development and implementation of large, automated agricultural equipment, such as combine harvesters, which have replaced large numbers of farm workers.
The crops grown in the U.S., such as wheat, barley, and rye, are only partly edible. While the seeds or grains at the top of each plant are edible and useful for making products such as bread and cereal, the rest of the plant, which is known as the chaff, is inedible and has to be discarded. Before modern-day machines were developed, such as in the 1800's, agricultural workers had to harvest crops by carrying out a series of laborious operations one after another. First they had to cut down the plants with a long-handled cutting tool such as a scythe. Next, they had to separate the edible grain from the inedible chaff by beating the cut stalks in an operation known as threshing. Finally, they had to clean any remaining debris away from the seeds to make them suitable for use in a mill. All this took a considerable amount of time and labor requiring large numbers of farm workers. The modern combine harvester carries out these various operations automatically eliminating the need for numerous farm workers.
In operation, a combine harvester is driven through a field of a growing crop, whereby the combine harvester cuts, threshes, and separates the grain from the chaff using rotating blades, wheels, sieves, and elevators. The grain collects in a tank inside the combine harvester, which is periodically emptied into tractors that drive alongside, while the chaff is ejected onto the field from an ejection spout at the back of the combine harvester.
In general, a combine harvester includes a header, a pickup reel, a cutter, a threshing drum, sieves, a collection tank, and conveyors, such as rotating belts and spinning augers. The header gathers the crop, and the pickup reel pushes the crop down toward the cutter, which cuts the crop at the base near ground level. A conveyor picks up the cuttings from the cutter, and conveys the cuttings to the threshing drum, which rotates and threshes the cuttings separating the grains from the chaff to form threshings, namely, the chaff and the separated grains. A conveyance conveys the threshings along the thresher from an upstream location of thresher to a downstream location of thresher as the thresher rotates and the grains fall through sieves into a collection tank inside the combine harvester, which is periodically emptied, such as into tractors that drive alongside, while a conveyor takes up and conveys the chaff to the ejection spout for ejection onto the field. Some combine harvesters have a rotating spreader mechanism that throws the chaff over a wide area, while others have bailers that bail the chaff for later use, such as for animal bedding.
Many threshing drums are formed with helical auger flights, which work to drive cuttings to the threshing drum for threshing. These auger flights forcibly rotate through the cuttings with the rotation of the threshing drum and are prone to substantial wear and damage, which necessitates regular flight repair or replacement. Repairing and replacing auger flights of threshing drums is expensive, time-consuming, and difficult, and results in costly downtime that most farmers simply cannot afford, thereby necessitating certain new and useful improvements in the art.